THE GIST

- The sound of a man's voice reveals his upper body strength and fighting ability.

- The findings put men on vocal par with many other animals whose calls also directly communicate body strength.

- Men's voices contain such information because ancestrally, men were more likely to engage in aggression.

A quick phone call to dad, or any other man, is far more revealing than previously thought, since new research has just determined that a human male's voice reveals his upper body strength, fighting ability, overall health, age, and emotional state.

Just hearing the sound of a man's voice, no matter what he is saying, communicates all of this information and more, according to the study, published in the latest Proceedings of the Royal Society B.

The findings put men on vocal par with red deer, common loons, baboons, croaking gourami fish, owls and other animals whose calls also directly communicate body strength and fighting ability.

"Ancestrally, a man's fighting ability would have been much more important to know as archaeological and anthropological evidence indicates that men were much more likely to engage in aggression than women were," Aaron Sell, lead author of the paper, told Discovery News.

"For that reason, it's very important to know how formidable a man is," added Sell, a researcher in the Center for Evolutionary Psychology at the University of California, Santa Barbara.

Sell and his colleagues took body and strength measurements from men and women belonging to four distinct populations: the Tsimane of Bolivia, Andean herder-horticulturalists, and U.S. and Romanian college students.

Each participant was asked to do things such as flex their biceps, which were measured, use a handgrip, and press a chest-strength muscle tester. The individuals also provided their fighting history, mentioning how many fights they had been in over the last four years.

The participants next spoke a certain sentence in their native language that was recorded. The American students, for example, were instructed to say, "When the sunlight strikes raindrops in the air, they act like a prism and form a rainbow." This sentence was extracted from what is known as "The Rainbow Passage," which includes every sound in the English language.

Undergraduates from UCSB rated the various voices on physical strength, height and weight. Their predictions were correct nearly every time for men, but not for women, even though many didn't even understand the language of the speakers. Both men and women listeners, however, were equally skilled at assessing the male voices.

"Information about male formidability would have been important for both sexes over evolutionary time," said Sell. "Both men and women would have benefitted from knowing who would likely win fights in order to make prudential alliances and for other reasons. Men would need this information to regulate their own fighting behavior. Women would also need this information in order to make effective mate choices."

There are a few exceptions to the voice/strength connection, however.

Sell pointed out that boxer Mike Tyson's voice does not match well with his physical power, and there are other men who sound very tough but may be scrawny. Nevertheless, such exceptions are few and far between, he suggests.

Another new study conducted by Sarah Wolff and David Puts from the Department of Anthropology at Pennsylvania State University found that men with deep, resonant, and "masculine" voices are viewed by other men as being more dominant. But the more dominant a man thinks he is, the less dominant he rates his rival's voices.

Sell and his colleagues could not precisely pinpoint what qualities in a man's voice indicate strength. He thinks it is probably a very complex mixture of features, comparable to those used to process facial attractiveness.

Men may no longer have to engage in physical fighting to climb up the social ladder, but the ability to evaluate a man's strength just based on his voice alone remains.

"Evolution works very, very slowly, especially on very large populations like ours," Sell said. "I wouldn't expect this ability to disappear anytime soon."